GLOBAL PATTERNS OF ORGANIC-WALLED PHYTOPLANKTON BIODIVERSITY DURING THE LATE SILURIAN TO EARLIEST DEVONIAN

Abstract

Abstract Numerous environmental factors as well as oceanic circulation patterns and geographic constraints all contribute to the abundance, distribution, and diversity of present-day marine phytoplankton assemblages. These same factors presumably affected the Paleozoic marine phytoplankton, which was dominated by organic-walled acritarchs and prasinophytes. During the Late Silurian (Gorstian, Ludfordian, and Přidoli) and earliest Devonian (Lochkovian), important paleogeographic, paleooceanographic, and geochemical changes were occurring as well as major compositional changes and diversity fluctuations in the marine organic-walled phytoplankton. Innovative morphologies appeared during the Late Silurian, in both low and high latitude assemblages, but with significant quantitative differences. This was followed by a turnover in assemblage composition during the Silurian/Devonian transition, and an initial radiation of new acritarch and prasinophyte taxa in the Early Devonian. Observed changes in total phytop...